Removable electrode bushings



Aug. 15,1967 AHEISL R I 3,336,061

REMOVABLE ELECTRODE BUSHI NGS Filed March 4, 1965 D's-A.

INVENTOR. RAYMOND A. HEISLER AGENT United States Patent Ofilice 3,336,061 REMOVABLE ELECTRODE BUSHINGS Raymond A. Heisler, Franklin Lakes, NJ. (122 Surrey Drive, Wayne, NJ. 07470) Filed Mar. 4, 1965, Ser. No. 437,212 2 Claims. (Cl. 287116) ABSTRACT OF THE DISCLOSURE A removable electrode bushing assembly for releasably gripping a shoulderless ceramic electrode holder and having a preformed resilient bushing with frustoconical ends This invention relates to a removable bushing for use in electrode holders and particularly for holders for electrodes as are used in the ignition of gun-type oil burners.

Even more particularly this invention relates to improvements in electrode holders of ceramic composition and requiring a shoulder or stop means for the mounting thereof in a holding means adapted for the mounting of the holder in a combustion wall.

Electrode holders as conventionally formed are made of ceramic composition and are fired to produce the optimum resistance to heat and shock. To retain these holders in a fixed position in the combustion wall there has heretofore been formed on this holder a circumferential shoulder portion. In the mounting of this holder in a screw-type mounting means it often occurs that excessive pressure is applied to this ceramic shoulder with this excessive pressure resulting in a cracked or broken holder thereby requiring disassembly and replacement. It is to be noted that the repair or replacement of a conventional fixed-shoulder electrode holder requires that a like elec- 'trode holder having the same shoulder to end dimension be used. This maintaining of the fixed dimension is necessary so that the geometry of combustion firing can be maintained.

It is an object of this invention to provide a removable and adjustable bushing for mounting on and retaining a ceramic electrode holder having no shoulder integral therewith. It is a further object of this invention to provide an electrode holder having an infinitely variable longitudinal adjustment for easy installation. It is a further object of this invention to provide a removable bushing adapted to be used on tubular electrode holders of diiferent lengths to provide a high degree of adaptability to varying installation conditions.

The attainment of these and other objects are provided in the instant invention which utilizes a pre-formed asbestos bushing of predetermined resiliency and metal retaining shells which retain and compress the asbestos bushing when the metal shells are urged toward each other. The pre-formed asbestos bushing contemplated for this invention has its sides sloped and has a circular passageway formed through the bushing, the passageway adapted to slide on a ceramic electrode holder of predetermined size. These metal retaining shells are adapted to slide freely on the ceramic electrode holder and to engage the side and outer periphery of the asbestos bushing. In installation and use the metal shells are urged toward each other whereby the shells compress the asbestos 3,336,061 Patented Aug. 15, 1967 and urge the asbestos into a firm gripping non-slip engagement with the tubular ceramic electrode holder.

There has thus been outlined rather broadly the most important features of the present invention in order that a detailed description thereof that follows may be better understood and in order that the present contribution to the art may be better appreciated. There are, of course, additional features of the invention that will be described hereafter and which will form the subject of claims appended hereto. Those persons skilled in the art will appreciate that the conception on which the present disclosure is based may readily be utilized as the basis for designing other structures for carrying out the several purposes of this invention. It is important, therefore, that the claims be regarded as including such equivalent constructions as do not depart from the concept and scope of this invention.

' A preferred and alternate embodiment of the invention has been chosen for purposes of illustration and description, and is shown in the accompanying drawing forming a part of the specification wherein:

FIG. 1 represents a cross-sectional side view of the assembly of one embodiment of this invention;

FIG. 2 represents an exploded cross-sectional side view of the components forming the removable bushing of FIG. 1;

FIG. 3 represents a cross-sectional side view of the assembly of an alternate embodiment of this invention;

FIG. 4 represents an exploded cross-sectional side view of the components forming the removable bushing of FIG. 3; and

FIG. 5 represents a side view partly in cross-section of the assembly of a conventional electrode holder and retaining means.

Referring now particularly to the drawing and the several views wherein similar characters designate corresponding parts throughout, the general arrangementof the preferred removable bushing is seen in FIGS. 1 and 2 wherein a tubular electrode holder 10 has a relatively constant outside diameter. The internal bore of the holder 10 generally has longitudinal grooves to accept shouldered portions on the shanks of electrodes. The electrode holder 10 forms no part of this invention except that it has a new outside configuration in which there is no shoulder integrally formed as a part thereof. Slidable on the outer diameter of holder 10 is a bushing 12 of asbestos or similar heat resistant resilient material which is made semi-rigid when molded. The resulting bushing after molding has a flow characteristic similar to a rubber composition having a resilience substantially equal to that of sixty durometer (Shore). The durometer, however, may vary from a reading of forty to eighty points. The sides 14 of the bushing 12 are sloped so that in cross-section the bushing has a truncated shape. The outside diameter 16 of this bushing is of a predetermined size and is made relatively concentric with the bore. Cooperating with the bushing are two end retaining shells 18a and 18b preferably stamped and drawn from sheet metal each having a bore 20 adapted to slide freely on the outer diameter of holder 10. Sloped sides 22 forming a conical member extend outwardly to a point substantially equal to the outer diameter 16 of the bushing 12. From this side 22 there extends a short cylindrical shoulder portion 24, the internal diameter of which is adapted to engage and retain the outer diameter 16 of bushing 12. It is to be noted that the slope of side 22 is greater than the slope of side 14, the purpose of this slope differential to be described hereafter.

In FIGS. 3 and 4 is shown an alternate embodiment in which a bushing 12 has sloped sides 14 and an outer diameter 16. The bushing of this embodiment is preferably similar in all essential characteristics and size as the bushing of FIGS. 1 and 2. A two-piece retaining shell in which one member is a long portion 30 and the other member is an end cone 32 is preferably made of stamped and drawn sheet metal. Each member piece has a bore 34 adapted to slide freely on the outer diameter of holder 10. Sloped sides 36 forming a conical portion extends outwardly from the bore 34 to a point substantially equal to the outer diameter 16 of the bushing 12. Long shell portion 30 has extending from the side 36 a cylindrical shoulder 38 the internal diameter of which is adapted to engage and retain the outer diameter 16 of bushing 12. The length of the shoulder 38 being sufficient to cover nearly the entire length of the exterior diameter 16. The outer diameter 40 of end cone 32 is adapted to slide into the internal diameter of the shoulder 38. As in FIGS. 1 and 2 the slope of sides 36 is greater than the slope of side 14, this slope differential to be described hereafter.

Referring now to FIG. 5 it is to be noted that a conventional electrode holder 50 has formed integral therewith a shoulder portion 52. A housing bushing 54 having threaded portion 55 for mounting in the wall of a combustion unit also has a sloped shouldered recess with a threaded portion adapted to receive an internally tapered nut 56. To use this holder 50 the service man making the installation must not only have a holder with the properly shaped and sized shoulder 52 but must also have this shoulder spaced a precise distance from the end 58 so that the to-be-installed electrode (not shown) will protrude a prescribed distance into the combustion chamber.

Use and operation of new electrode holder and bushing To use the electrode holder and bushing of this invention as seen in FIGS. 1 and 2 an electrode holder is selected having an outside diameter adapted to slide in the passageways of both housing bushing 54 and tapered nut 56. This holder is also selected of an overall length to accommodate the mounting therein of an electrode. An asbestos bushing 12 and a pair of end shells having a sliding fit on the holder 10 are arranged as in FIG. 2 and are then slid onto the holder 10. The holder, shells and bushing are then inserted into the recess in the housing bushing 54. Nut 56 is then slid onto the holder 10, the threads engaged and the nut turned into the housing bushing to lightly compress bushing 12. At this stage, holder 10 can be moved longitudinally in the bushing 12 and is so manipulated by the operator until the tip end of the holder 10 is positioned at the desired distance from the firewall of the combustion chamber. Nut 56 is then tightened in housing 54 the sloped sides 22 of the inwardly moved shells 18 causing the length of the outside diameter 16 of bushing 12 to be compressed and displaced. The displaced asbestos material being urged against holder 10 thereby locking the holder in longitudinal position and also providing a gas tight seal.

In like manner the asbestos bushing 12 and shell members 30 and 32 are assembled as in FIG. 4 and placed on holder 10 for installation in housing 54 and by nut 56. After tightening the nut 56 as in FIG. 3 the holder 10 is longitudinally locked in position, the compressed bushing 12 retaining the holder and providing as well a gas tight seal.

It is to be noted that the shells 18 and shells 30 and 32 are adapted to seat in a conventional housing 54. Nut 56 when used therewith provides a compressible recess having sloped shoulders of predetermined angle. Assuw ing that the slope of the walls 22 and 36 is about thirtyseven degrees the slopes of the walls 14 of bushing 12 is preferably made about thirty degrees. This provides that the displaced material of the bushing 12 will tend to flow inwardly. It is possible also to make the sides 14 and walls 22 and 36 of substantially the same angular slope and to cause the bushing to be compressed inwardly by using more force to urge the shells toward one another, the bushing 12 being captured by the end shells 18 or shells 30 and 32. The locking of holder 10 in the desired position is effected by causing bushing 12 to be compressed and the displaced material in the bushing to flow toward and around holder 10. In FIG. 1 over-tightening of nut 56 is prevented by predetermining the length of cylindrical shoulder 24 and allowing the ends thereof to meet and to thereby limit the maximum compression of bushing 12. In the embodiment of FIG. 3 a spacer 60 shown in phantom outline is disposed between housing 54 and nut 56 and provides a simple provision of a limiting means for the inward movement of nut 56. Spacer 60 can be made of laminated shim stock to accommodate variations of manufacture that may be experienced in field conditions.

While I have herein shown and described my invention in what I have conceived to be the most practical and preferred embodiment, it is recognized that departures may be made therefrom within the scope of my invention, which is not to be limited to the details disclosed herein but is to be accorded the full scope of the claims so as to embrace any and all equivalent devices.

Having described my invention herein, what I claim as new and desire to secure by Letters Patent is:

1. A removable electrode bushing assembly for use with a shoulderless electrode holder and adapted for mounting in a housing and nut assembly, said bushing assembly slidably mountable on the holder to provide a shoulder at an infinitely variable distance from the distal end of the holder, said bushing assembly comprising: (a) a resilient bushing of heat resistant material having a bore and an outside diameter relatively concentric to said bore, and having the ends sloped toward each other and formed as frustoconical surfaces; (b) a pair of metal end shells slidable on the holder and each having a frnstoconical end wall surface of a greater angle than the end surfaces of the bushing, one of the end shells having a length of outer cylindrical wall portion extending from an end wall a distance substantially equal to the length and size of the outer diameter of the resilient bushing, and the other end shell adapted to slide Within the cylindrical wall portion of the first shell, said other shell seated between the bushing and nut with the bushing disposed between the shells so that when the shells are urged toward each other by manipulation of the housing nut the shells will engage the resilient bushing to partially deform the bushing to cause a portion thereof to be displaced inwardly toward the shoulderless holder, and (c) a spacer of predetermined thickness between the housing and nut so as to limit the inward movement of the inner end of nut against the end shells and the resulting compression and deformation of the bushing toward the shoulderless holder.

2. A removable electrode bushing assembly as in claim 1 in which the resilient bushing is made of asbestos having a resiliency within a range of forty to eighty durometer (Shore).

References Cited UNITED STATES PATENTS 753,567 3/1904 Giles 277- 1,955,831 4/1934 Raybould 277212 2,333,580 11/1943 Renshaw et al 174--65 X 2,468,946 5/ 1949 Sherman.

FOREIGN PATENTS 268,162 3/ 1927 Great Britain. 434,020 8/ 1935 Great Britain.

CARL W. TOMLIN, Primary Examiner.

A. V. KUNDRAT, Assistant Examiner. 

1. A REMOVABLE ELECTRODE BUSHING ASSEMBLY FOR USE WITH A SHOULDERLESS ELECTRODE HOLDER AND ADAPTED FOR MOUNTING IN A HOUSING AND NUT ASSEMBLY, SAID BUSHING ASSEMBLY SLIDABLY MOUNTABLE ON THE HOLDER TO PROVIDE A SHOULDER AT AN INFINITELY VARIABLE DISTANCE FROM THE DISTAL END OF THE HOLDER, SAID BUSHING ASSEMBLY COMPRISING: (A) A RESILIENT BUSHING OF HEAT RESISTANT MATERIAL HAVING A BORE AND AN OUTSIDE DIAMETER RELATIVELY CONCENTRIC TO SAID BORE, AND HAVING THE ENDS SLOPED TOWARD EACH OTHER AND FORMED AS FRUSTOCONICAL SURFACES; (B) A PAIR OF METAL END SHELLS SLIDABLE ON THE HOLDER AND EACH HAVING A FRUSTOCONICAL END WALL SURFACE OF A GREATER ANGLE THAN THE END SURFACES OF THE BUSHING, ONE OF THE END SHELLS HAVING A LENGTH OF OUTER CYLINDRICAL WALL PORTION EXTENDING FROM AN END WALL A DISTANCE SUBSTANTIALLY EQUAL TO THE LENGTH AND SIZE OF THE OUTER DIAMETER OF THE RESILIENT BUSHING, AND THE OTHER END SHELL ADAPTED TO SLIDE WITHIN THE CYLINDRICAL WALL PORTION OF THE FIRST SHELL, SAID OTHER SHELL SEATED BETWEEN THE BUSHING AND NUT WITH THE BUSHING DISPOSED BETWEEN THE SHELLS SO THAT WHEN THE SHELLS ARE URGED TOWARD EACH OTHER BY MANIPULATION OF THE HOUSING NUT THE SHELLS WILL ENGAGE THE RESILIENT BUSHING TO PARTIALLY DEFORM THE BUSHING TO CAUSE A PORTION THEREOF TO BE DISPLACED INWARDLY TOWARD THE SHOULDERLESS HOLDER, AND (C) A SPACER OF PREDETERMINED THICKNESS BETWEEN THE HOUSING AND NUT SO AS TO LIMIT THE INWARD MOVEMENT OF THE INNER END OF NUT AGAINST THE END SHELLS AND THE RESULTING COMPRESSION AND DEFORMATION OF THE BUSHING TOWARD THE SHOULDERLESS HOLDER. 